The Latest: Serena says her shoulder starting to feel better

FILE - In this June 3, 2016, file photo, Serbia's Novak Djokovic returns the ball to Austria's Dominic Thiem during their semifinal match of the French Open tennis tournament at the Roland Garros stadium, in Paris. The U.S. Open tennis tournament begins Monday, Aug. 29. (AP Photo/Michel Euler, File)
(The Associated Press)

FILE - In this Aug. 12, 2016, file photo, Rafael Nadal, of Spain, returns during his match against Thomaz Bellucci, of Brazil, during their quarterfinal round match at the 2016 Summer Olympics in Rio de Janeiro, Brazil. The U.S. Open tennis tournament begins Monday, Aug. 29. (AP Photo/Charles Krupa, File)
(The Associated Press)

Andy Murray, of Britain, speaks during a media availability for the U.S. Open at the Billie Jean King National Tennis Center, Friday, Aug. 26, 2016, in New York. (AP Photo/Bryan R. Smith)
(The Associated Press)

Top-ranked Serena Williams says she hasn't practiced much because of her right shoulder injury.

Williams was struggling physically during her third-round loss at the Olympics and pulled out of the hard-court warmup in Cincinnati because of the shoulder problem. She said Friday that "I'm just now starting to feel a little bit better."

The American says she was able to practice for only two days before the Rio Games after the shoulder started bothering her following her Wimbledon victory. She says she is doing a lot of physical therapy.

Williams is seeking her 23rd major title, which would break a tie with Steffi Graf for most in the Open era.

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1:20 p.m.

Top-ranked Novak Djokovic says he injured his left wrist in Rio de Janeiro a few days before the start of the Olympic tournament.

The right-handed Djokovic needs that wrist for his backhand. He said Friday he's "getting there" and hopes he'll be "as close to 100 percent as possible" when he starts to defend his U.S. Open title.

The 12-time major champ also said his issues at Wimbledon weren't physical, but "there were other things I was going through." He declined to elaborate on those problems other than to say they had been resolved.

After Djokovic was upset in the third round of Wimbledon by 41st-ranked Sam Querrey, he was asked if he was 100 percent healthy, replying "not really" but not going into details.

Djokovic lost in the first round at the Rio Games to 2009 U.S. Open champ Juan Martin del Potro, whose ranking slipped because of left wrist problems of his own. Djokovic then pulled out of the hard-court warmup at Cincinnati, the first time he'd cited an issue with the wrist.

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12:35 p.m.

Top-ranked Serena Williams will meet two-time major semifinalist Ekaterina Makarova in the first round of the U.S. Open as the American seeks a record 23rd Grand Slam title.

Makarova made two straight major semis at the 2014 U.S. Open, losing to Williams, and the 2015 Australian Open. Her ranking has slipped to 36th, and she just missed a seed at Flushing Meadows. The Russian is coming off an Olympic doubles gold medal.

Williams could face fourth-seeded Agnieszka Radwanska in the semifinals, which is also when she could potentially meet sister Venus. Australian Open champ Angelique Kerber and French Open winner Garbine Muguruza are in the other half of the draw, which was set Friday.

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12:05 p.m.

Top-ranked Novak Djokovic faces 2013 Wimbledon semifinalist Jerzy Janowicz in the first round of the U.S. Open.

Janowicz has been ranked has high as 14th but has struggled in recent years and missed much of this season because of injuries. He's currently ranked 228th and used a protected ranking to get into the U.S. Open.

Friday's draw set Djokovic and Rafael Nadal as potential semifinal opponents, while Andy Murray and Stan Wawrinka are in the other half of the bracket.

Olympic silver medalist Juan Martin del Potro could face 19th-seeded American Steve Johnson in the second round. Ranked No. 142 because of three left wrist surgeries, the 2009 U.S. Open champ got in with a wild card.

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11:10 a.m.

American Sloane Stephens has withdrawn from the U.S. Open because of a right foot injury.

The announcement Friday means that Olympic gold medalist Monica Puig becomes the 32nd and final seed, as Stephens had been seeded 24th. Had Puig remained unseeded, she could have met one of the top players in the first or second round.

The 23-year-old Stephens was a 2013 quarterfinalist at Flushing Meadows and reached the semifinals at the Australian Open that year. While she had more success earlier in her career in the Grand Slams than in other tour events, that pattern had reversed in the last couple of years.

Stephens hadn't played since losing in the first round at the Olympics.

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9:45 a.m.

When the U.S. Open draw sets the first-round matchups, a top player could find himself with a daunting task.

Olympic silver medalist Juan Martin del Potro is unseeded at the year's final major, which starts Monday. Del Potro is ranked No. 142 because three left wrist surgeries forced him to miss so much time. The 2009 U.S. Open champ needed a wild card to get into the tournament.

So Friday's draw could put him in position to face a seeded player in the first or second round. That's what happened to top-ranked Novak Djokovic at the Olympics, when he lost to del Potro in his opening match. It's possible they could meet again early at Flushing Meadows.

Del Potro has defeated three of the U.S. Open's top four seeds since the start of Wimbledon.